The most common and most likely answer to this crossword clue is the 6 letter word POSTAL
P
O
S
T
A
L
More clues leading to the result POSTAL
- Job almost entirely involving the mail
- East German in China gets this sort of vote?
- Job confronting a student of letters
- Job facing a student of letters
- Mail-related job given to a learner
- Mail service to Alps is transformed
- AP lost out — it's mail-related
- After a line of mail
- Page found on a type of office file's a letterhead relating to mail service
- Second student drafting answers initially by mail
Buddy explains!

The straight part
We know that "Mail service" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case mail service = postal.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does POSTAL mean?
POSTAL adjective- Relating to the collection, sorting and delivery of mail.